System for recovering and treating waste water

ABSTRACT

This invention provides a compact effluent water reclamation apparatus which is minimized in the kinds and amounts of chemicals to be used for the recovery of water to thereby reduce the amount of waste and eliminate equipment which necessitates a large area for installation. The effluent water reclamation apparatus comprises a reverse osmosis device and is adapted to treat acid-alkali effluent water containing organic matter but no fluorine, by concentrating the acid-alkali effluent water containing organic matter by reverse osmosis, evaporating the resulting concentrated water to dryness and collecting the water permeating through a reverse osmosis membrane. The apparatus is characterized in that the apparatus comprises as arranged upstream from the reverse osmosis device a neutralizing device for neutralizing the effluent water to prevent a scale component from separating out from the effluent water in the process of reverse osmosis, and a biological treatment tank for biologically treating the neutralized effluent water.

TECHNICAL FIELD

The present invention relates to apparatus for reclaiming industrialeffluent water, i.e., acid-alkali effluent water containing organicmatter, and more particularly to apparatus for reclaiming effluent watercontaining ammonia and organic matter at relatively low concentrations,fluorine as the case may be, and further phosphoric acid, especially theeffluent water to be discharged from the wet process practiced with useof ultrapure water in plants for manufacturing semiconductors, liquidcrystals or like electronic products or devices.

BACKGROUND ART

When acid-alkali effluent water containing several ppm of organic matteris to be reclaimed, the effluent water is first neutralized in aneutralizing tank and thereafter treated in a biological treatment tankto decompose and remove the organic matter as shown in FIG. 3. Thebiologically treated water is subsequently supplied to anultrafiltration (UF) circulation tank and then to a UF device to removean SS component consisting mainly of microorganisms and contained in thetreated water. The biologically treated water resulting from the removalof SS is fed to a regenerative ion exchange device for the removal ofinorganic ions. The treated water free from inorganic ions is reused asrecycled water from waste water or water for replenishing a coolingtower.

In the flow chart of FIG. 3, each reference numeral stands for asfollows.

51; collected effluent

52; neutralizing agent

53; oxygen dissolving tank

54; UF circulation tank

55; air

56; regenerative ion exchange device

The other reference numerals are the same as those of FIG. 1.

In the case of fluorine-containing effluent water, slaked lime is firstadded to the collected effluent water in a reactor for the primarytreatment of the effluent water as shown in FIG. 4. CaF₂ is formedaccording to the reaction formula:

Ca²+2F⁻→CaF₂

to precipitate in a settling tank, and sludge containing the precipitateis removed with a dehydrator. On the other hand, the water resultingfrom the primary treatment is treated in a biological treatment tank todecompose and remove organic matter. Aluminum sulfate serving as acoagulant is further added to the biologically treated water in areactor for advanced treatment. Al(OH)₃ having a fluorine adsorbingproperty and formed according to the reaction formula:

Al³⁺+3OH→Al(OH)₃

is caused to adsorb the fluorine, followed by precipitation in asettling tank. The resulting sludge containing the Al(OH)₃ is removedwith the dehydrator. The fluorine contained in a very small amount inthe water subjected to the advanced treatment is removed by adsorptionin a adsorption column packed with a chelate resin. The water treated isdischarged from the column.

In the flow chart of FIG. 4, each reference numeral stands for asfollows.

61; flourine-containing collected effluent

62; slaked lime

63; settling tank

64; dehydrator

65; aluminum sulfate

66; sludge

67; discharge

The other reference numerals are the same as those of FIG. 1.

The apparatus for reclaiming acid-alkali effluent water containingseveral ppm of organic matter includes a regenerative ion exchangedevice as described above. This device requires regeneration of theresin when ions are adsorbed to saturation. Usually 2 or 3 equivalentweights of a regenerant is used for removing one equivalent weight ofions and discharged from the device, while the regeneration discharges alarge quantity of effluent. This gives rise to a need to suitably treatthe effluent additionally.

The apparatus for reclaiming effluent water containing organic matterdevelops troubles such as clogging of the separation membrane device orion exchange device disposed at a downstream location because theorganic matter in the collected effluent permits active growth ofmicroorganisms or because the metabolites of microorganisms, or fungiwill leak.

On the other hand, slaked lime for use in treating fluorine-containingeffluent water is in the form of fine particles and produces fineparticles of CaF₂ through a liquid-phase reaction when dissolved inwater. For a further advanced treatment of the effluent water, there isa need to add a coagulant to the water. The sludge produced by the useof these chemicals must be separated off by equipment such as acoagulation tank and thickener. The equipment then requires a large areafor installation. To reduce the fluorine concentration of the treatedwater below the effluent regulation level, slaked lime serving as aneutralizing agent, aluminum sulfate as a coagulant,high-molecular-weight coagulant, etc. need to be used in excessiveamounts, consequently producing a large quantity of sludge and adding tothe amount of waste to be discarded. The sludge contains about 80% ofwater even when dewatered, and the CaF₂ content of the sludge is usuallyup to 10%.

The water recovered still remains to be treated for use as the raw waterto be supplied to the pure water system resorting to conventional ionexchange and membrane separation.

An object of the present invention is to provide a compact effluentwater reclamation apparatus which is minimized in the kinds and amountsof chemicals to be used for the recovery of water to thereby reduce theamount of waste and eliminate equipment, such as a thickener, whichnecessitates a large area for installation.

Another object of the invention is to provide an effluent waterreclamation apparatus which is adapted for continuous treatment free ofthe likelihood of a membrane separation device or ion exchange devicebecoming clogged with microorganisms.

DISCLOSURE OF THE INVENTION

The present invention provides a first effluent water reclamationapparatus comprising a reverse osmosis device and adapted to treatacid-alkali effluent water containing organic matter but no fluorine.The first apparatus concentrates acid-alkali effluent water containingorganic matter by reverse osmosis, evaporates the resulting concentratedwater to dryness and collects the water permeating through a reverseosmosis membrane. The apparatus is characterized in that the apparatuscomprises as arranged upstream from the reverse osmosis device aneutralizing device for neutralizing the effluent water to prevent ascale component from separating out from the effluent water in theprocess of reverse osmosis, and a biological treatment tank forbiologically treating the neutralized effluent water.

With the first effluent water reclamation apparatus, fluorine-freeeffluent water is neutralized, for example, with an aqueous solution ofcaustic soda at a position upstream from the reverse osmosis device soas to render the effluent water unlikely to permit a scale component toseparate out (to give high solubility) even if the water is concentratedto an extreme extent with the reverse osmosis device. The neutralizedeffluent water is treated in the biological treatment device todecompose and remove the organic matter. The biological treatment tankhas an activated carbon packed layer which is fully supplied with oxygenor which is fluidized while being supplied with oxygen. Ammonia isdigested in the biological treatment tank when contained in the effluentwater. The pH of the effluent water drops during the process ofdigestion, so that the water is neutralized with an aqueous solution ofcaustic soda. The treated water flowing out from the biologicaltreatment tank contains an SS component consisting predominantly ofbacterial cells, so that the SS component is removed with anultrafiltration (UF) device. The ultrafiltration (UF) membrane to beused is one having special spacers adapted to prevent adhesion of orclogging with bacterial cells, such as Preprox UF membrane, product ofKurita Water Industries, Ltd. Alternatively available is a method ofconducting the biological treatment and removing the SS component in asingle tank, by immersing a microfiltration (MF) membrane in abiological treatment tank wherein an activated carbon layer is fluidizedwith a supply of oxygen and sucking the effluent water through the MFmembrane to obtain permeating water. The biologically treated waterresulting from the removal of the SS component has high solubility andcan therefore be concentrated with a reverse osmosis (RO) device to anextreme extent, for example, to {fraction (1/40)} of the amount oftreatment (permeating water 97.5, concentrated water 2.5 when the amountof treatment is taken as 100). The reverse osmosis (RO) membrane is, forexample, SE-10, product of Nitto Denko Corp. The water concentrated toan extreme extent is fed to an evaporator-dryer, whereby the sludgecomponent is evaporated to dryness. The evaporator-dryer is, forexample, a drum dryer. The water permeating through the reverse osmosismembrane is collected for reuse as recycled water from waste water,water for replenishing a cooling tower or raw water for the distillationpure water system.

The present invention provides a second effluent water reclamationapparatus comprising a reverse osmosis device and adapted to treatacid-alkali effluent water containing fluorine in addition to organicmatter. The second apparatus concentrates acid-alkali effluent watercontaining organic matter and fluorine by reverse osmosis, evaporatesthe resulting concentrated water to dryness and collects the waterpermeating through a reverse osmosis membrane. The apparatus ischaracterized in that the apparatus comprises a neutralizing devicedisposed upstream from the reverse osmosis device for neutralizing theeffluent water to prevent a scale component from separating out from theeffluent water in the process of reverse osmosis, a biological treatmenttank for biologically treating the neutralized effluent water, a calciumchloride adding device for adding calcium chloride to the concentratedwater resulting from the reverse osmosis, and an adsorption column forremoving fluorine ions from the water permeating through the reverseosmosis membrane.

The effluent water to be treated with the second apparatus can furthercontain phosphoric acid.

The fluorine-containing effluent water is treated by the secondapparatus in the same manner as the fluorine-free effluent water untilit is treated with the reverse osmosis device for concentration. Areactor is disposed upstream from an evaporator-dryer for adding CaCl₂to the concentrated water therein. Thus added to the water concentratedin the reverse osmosis device to an extreme extent is an aqueoussolution of calcium chloride in an amount approximately equivalent tothe fluorine concentration. The fluorine contained in the concentratedwater is converted into CaF₂ of low solubility in the reactor, and theCaF₂ produced is supplied to the evaporator and subjected to evaporationto dryness along with other sludge component. The conversion of thefluorine in the form of NaF as contained in the concentrated effluentwater into CaF₂ assures a facilitated drying procedure and ease ofhandling of the dried sludge. On the other hand, disposed downstreamfrom the reverse osmosis device is an adsorption column packed with anadsorber for removing fluorine from the water permeating through thereverse osmosis membrane. The adsorber is, for example, a chelate resinor zirconium adsorber. The permeating water having the fluorine adsorbedby the chelate resin for removal is collected and reused as recycledwater from waste water, water for replenishing the cooling tower or rawwater for the distillation pure water system.

The biological treatment tanks for use in the first and second effluentwater reclamation apparatus are preferably those for practicing thefluidized-bed biological activated carbon process. A microfiltration(MF) membrane can be provided in the treatment tank for separating theSS component from the treated water before feeding to the reverseosmosis device.

The present invention provides a third effluent water reclamationapparatus comprising an evaporator and adapted to treat acid-alkalieffluent water containing organic matter but no fluorine. The thirdapparatus concentrates acid-alkali effluent water containing organicmatter by evaporation, evaporates the resulting concentrated water todryness and collects the vapor in the form of water. The apparatus ischaracterized in that the apparatus comprises as arranged upstream fromthe evaporator a neutralizing device for neutralizing the effluent waterto prevent a scale component from separating out from the effluent waterin the process of concentration by evaporation, and a biologicaltreatment tank for biologically treating the neutralized effluent water.

The third apparatus and the treatment procedure thereof are basicallythe same as those of the first apparatus except that the reverse osmosisdevice of the first apparatus is replaced by the evaporator. With thethird apparatus, the device positioned downstream from the biologicaltreatment tank and upstream from the evaporator is mainly operated withheating and is free of troubles due to the presence of microorganisms.Accordingly an SS separator is disposed downstream from the biologicaltreatment device for separating the SS component from the treated water.The SS separator is preferably a centrifugal strainer, which is, forexample, one manufactured by IM Corporation. Examples of usefulevaporators are a multi-effect evaporator and a thermo-compressionevaporator.

The present invention provides a fourth effluent water reclamationapparatus comprising an evaporator and adapted to treat acid-alkalieffluent water containing fluorine in addition to organic matter. Thefourth apparatus concentrates acid-alkali effluent water containingorganic matter and fluorine by evaporation, evaporates the resultingconcentrated water to dryness and collects the vapor in the form ofwater. The apparatus is characterized in that the apparatus comprises aneutralizing device disposed upstream from the evaporator forneutralizing the effluent water to prevent a scale component fromseparating out from the effluent water in the process of concentrationby evaporation, a biological treatment tank for biologically treatingthe neutralized effluent water, and a calcium chloride adding device foradding calcium chloride to the concentrated water resulting from theprocess of concentration by evaporation.

The fourth apparatus and the treatment procedure thereof are basicallythe same as those of the second apparatus except that the reverseosmosis device of the second apparatus is replaced by the evaporator.With the fourth apparatus as in the third apparatus, the devicepositioned downstream from the biological treatment tank and upstreamfrom the evaporator can be a centrifugal strainer for removing the SScomponent, and the evaporator to be used is, for example, a multi-effectevaporator or thermo-compression evaporator.

The biological treatment tanks for use in the third and fourth effluentwater reclamation apparatus are preferably those for practicing thefluidized-bed biological activated carbon process. A microfiltration(MF) membrane can be provided in the treatment tank for separating theSS component from the treated water before feeding to a reverse osmosisdevice. When required, an adsorption column is provided in the fourthapparatus for removing fluorine ions from the water permeating throughthe reverse osmosis membrane.

The water obtained by the treatment in the first, second, third orfourth apparatus can be collected and mixed with replenishing industrialwater or city water for use as raw water for the distillation pure watersystem.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing a semiconductor wet process for use inExample 1.

FIG. 2 is a flow chart showing a semiconductor wet process for use inExample 2.

FIG. 3 is a flow chart showing a conventional procedure for treatingeffluent water containing organic matter.

FIG. 4 is a flow chart showing a conventional procedure for treatingeffluent water containing flourine.

BEST MODE FOR CARRYING OUT THE INVENTION

Examples of the present invention will be described below in detail withreference to effluent water reclamation systems for wet processes formanufacturing semiconductors with use of large amounts of chemicals andpure water. However, the invention is not limited to these examples.

The effluent water discharged from the wet process is collected asseparated into dilute effluent water, acid-alkali concentrated effluentwater and effluent water containing hydrofluoric acid and phosphoricacid. Table 1 shows the properties of these effluents.

TABLE 1 Properties of Rinsed Effluents from Semiconductor Wet ProcessesAcid-alkali Hydrofluoric, Effluent Dilute concentrated phosphoric acid-water water water containing water Water amt. 60 20 20 Conductivi- 602200 800 ty (μS/cm) TOC (ppm) 525 2200 2200 pH 2.8 2.3 2.7 Main H₂SO₄H₂SO₄ HF component H₂O₂ H₂O₂ NH₄F NH₄OH NH₄OH H₃PO₄ HCl HCl

Water amt., i.e., the amount of each effluent, is a value estimated whenthe amount of ultrapure water used is taken as 100.

EXAMPLE 1

With reference to FIG. 1, the raw water to be supplied to a distillationpure water system can be of rough properties unlike the material for thepure water system consisting essentially of an ion exchange device andmembrane filtration device, so that the dilute effluent is merelyadjusted in pH in a neutralizing tank and then collected in a raw watertank. The neutralizing agent to be used is an aqueous solution ofcaustic soda, which renders the effluent highly soluble and less likelyto permit a scale component to separate out in the concentration processof the distillation pure water system.

The acid-alkali concentrated effluent is first neutralized in aneutralizing tank so as not to interfere with the activity ofmicroorganisms in a biological treatment tank. The neutralizing agent tobe used is an aqueous solution of caustic soda for rendering theeffluent highly soluble and less likely to permit a scale component toseparate out in the concentration process of a reverse osmosis device.The effluent is about 620 μS/cm in conductivity after neutralization.

The neutralized acid-alkali concentrated effluent is fed to a biologicaltreatment tank for decomposing organic matter (TOC) and digestingammonia. The treating tank is provided at its bottom with aerationnozzles for uniformly aerating the entire tank. The tank containsactivated carbon which serves as a carrier for retaining microorganismsthereon and which is fluidized within the tank by the aeration. The tankfurther has an MF membrane immersed therein for separating an SScomponent from the biologically treated water to supply the resultingwater to a reverse osmosis device. The MF membrane is a flat membrane soshaped as to hold spacers between membrane portions, such that the waterto be treated is positioned outside the membrane, and the waterpermeating through the membrane flows through the spacers and istransported to a treated water tank by a suction pump. Since thedigestion of ammonia in the biological treating tank results in a lowerpH, an aqueous solution of caustic soda is placed into the treating tankto adjust the pH to 7. After the removal of the SS component, thebiologically treated water is about 660 μS/cm in conductivity and about660 ppb in TOC.

The biologically treated water resulting from the removal of the SScomponent is fed from the treated water tank to the reverse osmosisdevice, in which about 99% of inorganic ions are removed. The waterpermeating through the reverse osmosis membrane is 97.5% in recoveryratio, about 160 μS/cm in conductivity and about 550 ppb in TOC. Thepermeating water is collected in the raw water tank.

The water concentrated to 2.5% of the amount of water treated is about22000 μS/cm in conductivity and about 4850 ppb in TOC, and is fed to adrum dryer and evaporated to dryness. The solidified dry sludge isdisposed of as waste.

The effluent containing hydrofluoric acid and phosphoric acid is treatedin the same manner as the acid-alkali concentrated effluent until it istreated by reverse osmosis. The water resulting from the treating stepshas the following properties. The neutralized effluent is about 110μS/cm in conductivity, the biologically treated water as separated fromthe SS component is about 150 μS/cm in conductivity and about 660 ppb inTOC, the water permeating through the reverse osmosis membrane is about50 μS/cm in conductivity and about 550 ppb in TOC, and the waterconcentrated by reverse osmosis (RO) is about 5000 μS/cm in conductivityand about 4850 ppb in TOC. Since the water permeating through thereverse osmosis membrane contains about 1 ppm of fluorine ions and about10 ppm of phosphate ions, these ions are removed by adsorption in achelate resin adsorption column disposed downstream from the reverseosmosis device to reduce both the ion contents to about 0.1 ppm. Thewater is then collected in the raw water tank. Disposed upstream from anevaporator-dryer is a reactor wherein an aqueous solution of CaCl₂ isadded to the water concentrated by reverse osmosis to convert thefluorine therein in the form of NaF into CaF₂ to facilitate handling ofthe concentrate by the dryer and make the dried sludge easy to handle.The fluorine contained in the concentrated water is converted into CaF₂of low solubility in the reactor, and the fluoride is supplied to thedrum dryer and subjected to evaporation to dryness along with othersludge component. The solidified dry sludge is disposed of as waste.

The water resulting from the effluent treatments is collected in the rawwater tank and mixed with replenishing industrial water, and the mixtureis fed to a fluidized-bed biological activated carbon device, in whichthe mixture is treated by decomposition to TOC of about 160 ppb. Thewater treated by this device is about 150 μS/cm in conductivity andabout 160 ppb in TOC, and the water of this quality is satisfactory foruse as a feed to the distillation pure water system. The water treatedwith the biological activated carbon device is supplied to thedistillation pure water system and thereby made into primary pure waterwhich is 15 MΩ·cm in resistivity and 10 ppb in TOC. The primary water isfed to a subsystem and made into ultrapure water which is 18.2 MΩ·cm inresistivity and up to 1 ppb in TOC for use in the wet process formanufacturing semiconductors.

In the flow chart of FIG. 1, which shows procedure of Example 1, eachreference numeral stands for as follows.

1; cooling tower for entire plant

2; cooling tower for pure water system

3; primary pure water system

4; hot steam

4′; distillation pure water system

4″; steam drain

5; subsystem

6; pure water tank

7; cooling water

8; low-pressure UV

9; polisher

10; UF membrane

11; ultrapure water circulation pump

12; use points

13; dilute effluent system

14; water feed pump

15; neutralizing tank

16; neutralizing tank

17; biological treatment tank

18; suction pump

19; MF membrane

20; aeration

21; treated water tank

22; RO pump

23; RO membrane

24; hydrofluoric acid-phosphoric acid recovery system

25; reactor

26; adsorption column

27; industrial water

28; steam

29; drum dryer

30; evaporation to dryness

31; acid-alkali effluent recovery system (concentrated waste liquid)

32; raw water tank

33; raw water pump

34; activated carbon device

EXAMPLE 2

With reference to FIG. 2, the raw water to be supplied to a distillationpure water system can be of rough properties unlike the material for thepure water system consisting essentially of an ion exchange device andmembrane filtration device, so that the dilute effluent is merelyadjusted in pH in a neutralizing tank and then collected in a raw watertank. The neutralizing agent to be used is an aqueous solution ofcaustic soda, which renders the effluent highly soluble and less likelyto permit a scale component to separate out in the concentration processof the distillation pure water system.

The acid-alkali concentrated effluent is first neutralized in aneutralizing tank so as not to interfere with the activity ofmicroorganisms in a biological treatment tank. The neutralizing agent tobe used is an aqueous solution of caustic soda for rendering theeffluent highly soluble and less likely to permit a scale component toseparate out in the concentration process of an evaporator. The effluentis about 620 μS/cm in conductivity after neutralization.

The neutralized acid-alkali concentrated effluent is fed to a biologicaltreatment tank for decomposing organic matter (TOC) and digestingammonia. The treating tank is provided at its bottom with aerationnozzles for uniformly aerating the entire tank. The tank containsactivated carbon which serves as a carrier for retaining microorganismsthereon and which is fluidized within the tank by the aeration.

Since the digestion of ammonia in the biological treating tank resultsin a lower pH, an aqueous solution of caustic soda is placed into thetreating tank to adjust the pH to 7. After the removal of the SScomponent, the biologically treated water is about 660 μS/cm inconductivity and about 660 ppb in TOC.

Since the biologically treated water contains an SS component consistingpredominantly of bacterial cells, the SS component is removed with acentrifugal strainer. The devices arranged downstream from the treatingtank are mainly operated with heating, no trouble attributable tomicroorganisms will occur even if the centrifugal strainer is used forremoving the SS component.

The biologically treated water resulting from the removal of the SScomponent is fed from the treated water tank to the evaporator, in whichalmost all impurities (ion component) are concentrated. The recoveryratio achieved is 97.5%. The distilled water flowing out from theevaporator is about 1.5 μS/cm in conductivity and about 66 ppb in TOC.The distilled water is cooled in a heat exchanger to about 35° C. andcollected in the raw water tank.

The water concentrated to 2.5% of the amount of water treated is about25000 μS/cm in conductivity and about 5000 ppb in TOC, and is fed to adrum dryer and evaporated to dryness. The solidified dry sludge isdisposed of as waste.

The effluent containing hydrofluoric acid and phosphoric acid is treatedin the same manner as the acid-alkali concentrated effluent until it istreated by evaporation for concentration. The water resulting from thetreating steps has the following properties. The neutralized effluent isabout 110 μS/cm in conductivity, the biologically treated water asseparated from the SS component is about 150 μS/cm in conductivity andabout 660 ppb in TOC, the distilled water flowing out from theevaporator is about 0.5 μS/cm in conductivity and about 66 ppb in TOC,and the concentrated water egressing from the evaporator is about 5000μS/cm in conductivity and about 5000 ppb in TOC. The distilled waterfrom the evaporator contains about 0.03 ppm of fluorine and is thereforecooled as it is in a heat exchanger to about 35° C. and collected in theraw water tank. Disposed upstream from an evaporator-dryer is a reactorwherein an aqueous solution of CaCl₂ is added to the concentrated waterfrom the evaporator to convert the fluorine therein in the form of NaFinto CaF₂ to facilitate handling of the concentrate by the dryer andmake the dried sludge easy to handle. The fluorine contained in theconcentrated water from the evaporator is converted into CaF₂ of lowsolubility in the reactor, and the fluoride is supplied to the drumdryer and subjected to evaporation to dryness along with other sludgecomponent. The solidified dry sludge is disposed of as waste.

The water resulting from the effluent treatments is collected in the rawwater tank and mixed with replenishing industrial water, and the mixtureis fed to a fluidized-bed biological activated carbon device, in whichthe mixture is treated by decomposition to TOC of about 160 ppm. Thewater treated by this device is about 150 μS/cm in conductivity andabout 160 ppb in TOC, and the water of this quality is satisfactory foruse as a feed to the distillation pure water system. The water treatedby the biological activated carbon device is supplied to thedistillation pure water system and thereby made into primary pure waterwhich is 15 MΩ·cm in resistivity and 10 ppb in TOC. The primary water isfed to a subsystem and made into ultrapure water which is 18.2 MΩ·cm inresistivity and up to 1 ppb in TOC for use in the wet process formanufacturing semiconductors.

The chemicals to be used for the effluent water reclamation treatment ofthe present invention are limited only to an aqueous solution of causticsoda for neutralization, and aqueous solution of calcium chloride, whichis used when the effluent contains hydrochloric acid, and are fewer thanin the prior art. The chemicals to be added are each in the form of anaqueous solution, easer to handle and reactive at a higher velocity,hence no need to use an excess of the chemical. This renders thechemical usable at a reduced cost, and diminishes the amount of drysludge to be discharged.

Since there is no need to use equipment, such as a thickener, whichrequires a large area for installation, the apparatus is compact in itsentirety.

In the case of the third and fourth effluent reclamation apparatus, thedevices arranged downstream from the biological treatment device areoperated mainly with heating, can therefore be free of troubles due tomicroorganisms, rendering the apparatus operable continuously.

Effluent water can be reclaimed for reuse as pure water by using theeffluent water reclamation apparatus of the invention in combinationwith a distillation pure water system.

In the flow chart of FIG. 2, which shows procedure of Example 2, eachreference numeral stands for as follows.

40; centrifugal strainer

41; evaporator

42; heat exchanger

43, 44; cooling water

The other reference numerals are the same as those of FIG.1.

INDUSTRIAL APPLICABILITY

The present invention relates to apparatus for reclaiming industrialeffluent water, i.e., acid-alkali effluent water containing organicmatter, and more particularly to apparatus for reclaiming effluent watercontaining ammonia and organic matter at relatively low concentrations,fluorine as the case may be, and further phosphoric acid. The inventionrelates especially to apparatus for reclaiming the effluent water to bedischarged from the wet process practiced with use of ultrapure water inplants for manufacturing semiconductors, liquid crystals or likeelectronic products or devices.

What is claimed is:
 1. In a system for concentrating acid-alkalieffluent water containing organic matter by reverse osmosis, evaporatingthe resulting concentrated water to dryness and collecting the waterpermeating through a reverse osmosis membrane, an effluent waterreclamation apparatus comprises as arranged upstream from a reverseosmosis device a neutralizing device for neutralizing the effluent waterto prevent a scale component from separating out from the effluent waterin the process of reverse osmosis, and a biological treatment tank forbiologically treating the neutralized effluent water, the biologicaltreatment tank using a fluidized-bed biological activated carbonprocess, wherein the biological treatment tank is provided in itsinterior with a microfiltration membrane for separating an SS componentfrom the treated water, said microfiltration membrane being a flatmembrane shaped to hold spacers between membrane portions so that thewater to be treated is positioned outside the membrane.
 2. In a systemfor concentrating acid-alkali effluent water containing organic matterand fluorine by reverse osmosis, evaporating the resulting concentratedwater to dryness and collecting the water permeating through a reverseosmosis membrane, an effluent water reclamation apparatus comprises aneutralizing device disposed upstream from a reverse osmosis device forneutralizing the effluent water to prevent a scale component fromseparating out from the effluent water in the process of reverseosmosis, a biological treatment tank for biologically treating theneutralized effluent water, a calcium chloride adding device for addingcalcium chloride to the concentrated water resulting from the reverseosmosis, and an adsorption column for removing fluorine ions from thewater permeating through the reverse osmosis membrane, the biologicaltreatment tank using a fluidized-bed biological activated carbonprocess, wherein the biological treatment tank is provided in itsinterior with a microfiltration membrane for separating an SS componentfrom the treated water, said microfiltration membrane being a flatmembrane shaped to hold spacers between membrane portions so that thewater to be treated is positioned outside the membrane.
 3. An effluentwater reclamation apparatus according to claim 2 wherein the acid-alkalieffluent water further contains phosphoric acid.
 4. In a system forconcentrating acid-alkali effluent water containing organic matter byevaporation, evaporating the resulting concentrated water to dryness andcollecting the vapor in the form of water, and effluent waterreclamation apparatus comprises as arranged upstream from an evaporatora neutralizing device for neutralizing the effluent water to prevent ascale component from separating out from the effluent water in theprocess of concentration by evaporation, and a biological treatment tankfor biologically treating the neutralized effluent water, the biologicaltreatment tank using a fluidized-bed activated carbon process, whereinan SS separator is provided downstream from the biological treatmenttank for separating an SS component from the treated water, wherein theSS separator is a centrifugal strainer.
 5. In a system for concentratingacid-alkali effluent water containing organic matter and fluorine byevaporation, evaporating the resulting concentrated water to dryness andcollecting the vapor in the form of water, an effluent water reclamationapparatus comprises a neutralizing device disposed upstream from anevaporator for neutralizing the effluent water to prevent a scalecomponent from separating out from the effluent water in the process ofconcentration by evaporation, a biological treatment tank forbiologically treating the neutralized effluent water, and a calciumchloride adding device for adding calcium chloride to the concentratedwater resulting from the process of concentration by evaporation, thebiological treatment tank using a fluidized-bed activated carbonprocess, wherein an SS separator is provided downstream from thebiological treatment tank for separating an SS component from thetreated water, wherein the SS separator is a centrifugal strainer.
 6. Aneffluent water reclamation apparatus according to claim 5 wherein theacid-alkali effluent water further contains phosphoric acid.
 7. Aneffluent water reclamation process which uses an apparatus according toany one of claims 1, 2, 3, 5, or 6.